Shift switching device

ABSTRACT

An HV-ECU executes a program including a step (S 102 ) of turning on a fail-safe permission flag if a select sensor is abnormal (YES in step S 100 ), and a step (S 108 ) of transmitting a non-P request signal to a P-ECU if the position of a shift lever is read as the N position (YES in S 104 ) and a predetermined time Tn( 2 ) elapses (YES in S 106 ).

This is a divisional of application Ser. No. 12/601,400 filed Nov. 23,2009, which is a National Stage of International Application No.:PCT/JP2008/059965 filed May 23, 2008, the contents of all of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to control of a shift switching mechanism,and in particular to control of releasing a parking lock according tothe intention of a driver even in the event of an abnormality in asensor detecting the position of a shift lever.

BACKGROUND ART

Conventionally, as shift switching mechanisms switching a shift positionof an automatic transmission by an actuator according to manipulation ofa shift lever by a driver, those equipped with an electric motor (forexample, a direct current motor) as a motive power source for switchinga shift position have been known.

According to a shift switching mechanism as described above, there is noneed to mechanically connect a shift lever and the shift switchingmechanism as in a common switching mechanism that directly switches ashift position of an automatic transmission using manipulation forceapplied to a shift lever by a driver. Therefore, there is no limitationin layout when these components are mounted in a vehicle, and thus thedegree of freedom in design can be increased. Further, there has been anadvantage that mounting to a vehicle can be easily performed.

As a shift lever in such a shift switching mechanism, a momentary-typeshift lever may be used. In the momentary-type shift lever, switching toa drive position such as the R, N, D, or B position and switching fromthe P position is performed according to manipulation of the shift leverstarting from a reference position. The shift lever is provided with ashift sensor sensing movement of manipulation in a longitudinaldirection and a select sensor sensing movement of manipulation in alateral direction. Based on outputs from these sensors, a shift positionis determined.

As a shift lever as described above, for example, Japanese PatentLaying-Open No. 2005-7993 discloses a shift device of a transmissionappropriately responding to a driver's request in the shift device witha momentary function. The shift device of a transmission is a shiftdevice of a transmission including a path for reaching a plurality ofshift positions, and a momentary-type movable portion manipulated so asto move along the path by a driver. The movable portion is held at apredetermined reference position when it is not manipulated by thedriver. The shift device includes recognition means for recognizing ashift position requested by the driver from holding of the movableportion at the shift position for a predetermined recognition time, andoutput means for outputting a control signal to the transmission so asto attain a power transmission state corresponding to the recognizedshift position. The path includes the reference position, a first shiftposition representing one of the plurality of shift positions, and asecond shift position representing one of the plurality of shiftpositions and provided between the reference position and the firstshift position. When it is recognized that the movable portion islocated at the first shift position, the power transmission state by thetransmission is set to a first state. When it is recognized that themovable portion is located at the second shift position, the powertransmission state by the transmission is set to a second statedifferent from the first state. The shift device further includessetting means for setting the recognition time in accordance with amoving direction of the movable portion along the path.

According to the shift device of a transmission, a time for recognizingthe second shift position in a first case where the driver performsmanipulation based on a request to bring the power transmission state bythe transmission into the second state and the movable portion islocated at the second shift position, and a time for recognizing thesecond shift position in a second case where the movable portion comesto the second shift position on its way to return to the referenceposition can be set separately. Therefore, the driver's request canappropriately be recognized based on a time for which the movableportion is held at the second shift position.

However, if an abnormality occurs in a sensor during detection of theposition of a shift lever with a select sensor and a shift sensor, aparking lock cannot be released depending on the state of theabnormality. For example, in a case where an abnormality occurs in theselect sensor while it is detecting the position of the shift lever in adirection in which the shift lever is moved between the referenceposition and a neutral position, if it is unclear whether switching tothe neutral position is performed, there is a possibility that a parkingposition cannot be released.

This is because, when the select sensor is abnormal, if positiondetection by the select sensor is not performed after switching to theparking position is performed, or if it is unclear whether switching tothe neutral position is performed, it is also unclear whether switchingto a forward drive position or a reverse drive position is performed.Therefore, it is impossible to release the parking position according tothe intention of the driver when the select sensor is abnormal.

If it is impossible to release the parking position according to theintention of the driver, the parking lock cannot be released.Accordingly, for example, it is impossible to move a disabled vehicle bypushing the same with hands or using a tow truck or the like. In theaforementioned publication, the problems described above are notconsidered at all, and thus cannot be solved.

DISCLOSURE OF THE INVENTION

One object of the present invention is provide a shift switching devicethat releases a parking lock according to the intention of a driver evenin the event of an abnormality in a sensor detecting the position of ashift lever.

A shift switching device in accordance with an aspect of the presentinvention includes a first detection unit detecting a position of ashift lever moving along a shift gate in a first direction and a seconddetection unit detecting a position of the shift lever in a seconddirection, for switching a shift position of a transmission mounted in avehicle based on the position in the first direction and the position inthe second direction. The shift position includes at least a parkingposition. The shift switching device further includes a processing unitconnected to the first detection unit and the second detection unit. Theprocessing unit determines whether or not the first detection unit isabnormal, and in a case where the processing unit determines that thefirst detection unit is abnormal, the processing unit changes a shiftposition corresponding to a position of the shift lever to a shiftposition releasing the parking position.

According to the present invention, in a case where the first detectionunit is determined as abnormal, the position of the shift lever in thefirst direction cannot be detected. In this case, a shift positioncorresponding to a position of the shift lever is changed to a shiftposition releasing the parking position (for example, a neutralposition). For example, a shift position specified by detecting theposition in the second direction using the second detection unit ischanged to a shift position releasing the parking position. Thereby, theparking position can be reliably released by manipulating the shiftlever, and thus a parking lock can be released according to theintention of a driver. As a result, the vehicle can be moved by beingpushed with hands or using a tow truck or the like. Therefore, a shiftswitching device that releases a parking lock according to the intentionof a driver even in the event of an abnormality in a sensor detectingthe position of a shift lever can be provided.

Preferably, in a case where the first detection unit is abnormal and inaddition the shift position is the parking position, the processing unitchanges the shift position corresponding to the position of the shiftlever to the shift position releasing the parking position.

According to the present invention, in a case where the shift positionis the parking position, the parking lock is in an actuated state. Ifthe first detection unit is abnormal on this occasion, the position ofthe shift lever in the first direction cannot be detected. In a casewhere the first detection unit is abnormal and in addition the shiftposition is the parking position, the shift position corresponding tothe position of the shift lever is changed to the shift positionreleasing the parking position (for example, the neutral position). Forexample, the shift position specified by detecting the position in thesecond direction using the second detection unit is changed to the shiftposition releasing the parking position. Thereby, the parking positioncan be reliably released by manipulating the shift lever, and thus theparking lock can be released according to the intention of a driver.

More preferably, a reference position serving as a starting point ofmanipulation of the shift lever is set in the shift gate. In a casewhere the first detection unit is abnormal and in addition the positionof the shift lever is maintained at the reference position until apredetermined time elapses, the processing unit changes the shiftposition corresponding to the position of the shift lever to the shiftposition releasing the parking position.

According to the present invention, in a case where the position of theshift lever is maintained at the reference position until apredetermined time elapses, it can be determined that the shift lever isnot in a state of being erroneously manipulated. In this case, the shiftposition corresponding to the position of the shift lever is changed tothe shift position releasing the parking position (for example, theneutral position). Thereby, the parking position can be reliablyreleased by manipulating the shift lever, and thus the parking lock canbe released according to the intention of a driver.

More preferably, the shift position further includes a neutral positionand a plurality of shift positions related to driving of the vehicle. Ina case where the first detection unit is abnormal, the processing unitchanges at least one of the plurality of shift positions correspondingto the position of the shift lever specified by the position in thesecond direction when the first detection unit is abnormal, to theneutral position.

According to the present invention, in a case where the first detectionunit is abnormal, the processing unit changes at least one of theplurality of shift positions to the neutral position. If the firstdetection unit is abnormal, the position of the shift lever in the firstdirection cannot be detected. Therefore, at least one of the pluralityof shift positions related to driving of the vehicle (for example, aforward drive position, a reverse drive position, or the like) specifiedby detecting the position of the shift lever in the second direction ischanged to the neutral position. Thereby, the shift position can bereliably switched to the neutral position by manipulating the shiftlever. That is, switching from the parking position to the neutralposition can be performed even when there occurs an abnormality in thefirst detection unit. Therefore, the parking lock can be releasedaccording to the intention of a driver.

More preferably, the neutral position corresponds to a position at oneend of a range in which the shift lever is movable in the firstdirection.

According to the present invention, if the first detection unit isabnormal, the position of the shift lever in the first direction cannotbe detected. Accordingly, whether or not the shift position is moved tothe neutral position cannot be determined. In this case, for example, ifat least one of the plurality of shift positions related to driving ofthe vehicle specified by detecting the position of the shift lever inthe second direction is changed to the neutral position, the shiftposition can be reliably switched to the neutral position bymanipulating the shift lever. Therefore, the parking lock can bereleased according to the intention of a driver.

More preferably, the processing unit determines whether or not the firstdetection unit is abnormal based on a detection result of the firstdetection unit.

According to the present invention, whether or not the first detectionunit is abnormal can be determined with high accuracy.

More preferably, the first detection unit outputs a voltagecorresponding to the position of the shift lever in the first direction.The processing unit determines whether or not the first detection unitis abnormal based on a state of the output voltage.

According to the present invention, the processing unit determineswhether or not the first detection unit is abnormal based on the stateof the voltage output by the first detection unit (for example, theoutput voltage's fixation on a low side or fixation on a high side, adifference in output voltage values of two sensors, or the like).Thereby, whether or not the first detection unit is abnormal can bedetermined with high accuracy.

More preferably, in a case where the position of the shift leverspecified by the position in the first direction is not a positioncorresponding to the shift position of the transmission in relation tothe position in the second direction, the processing unit determinesthat the first detection unit is abnormal.

According to the present invention, in a case where the position of theshift lever specified by the position in the first direction is not aposition corresponding to the shift position of the transmission inrelation to the position in the second direction, the processing unitdetermines that the first detection unit is abnormal. Thereby, whetheror not there occurs an abnormality in the detection result of the firstdetection unit can be determined with high accuracy.

More preferably, the shift position further includes a neutral position.In the case where the position of the shift lever specified by theposition in the first direction is not the position corresponding to theshift position of the transmission in relation to the position in thesecond direction, the processing unit changes the shift positioncorresponding to the position of the shift lever to the neutralposition.

According to the present invention, in the case where the position ofthe shift lever specified by the position in the first direction is nota position corresponding to the shift position of the transmission inrelation to the position in the second direction, the processing unitchanges the shift position to the neutral position. Thereby, the shiftposition can be reliably switched to the neutral position bymanipulation of the shift lever by a driver even in the event of anabnormality in the first detection unit. Therefore, the parking lock canbe released according to the intention of the driver.

More preferably, if the position of the shift lever is maintained untila predetermined first time elapses, the shift switching device switchesthe shift position of the transmission to the shift positioncorresponding to the position of the shift lever, and in a case wherethe first detection unit is abnormal, if the position of the shift leveris maintained until a predetermined second time longer than the firsttime elapses, the shift switching device switches the shift position ofthe transmission to the shift position corresponding to the position ofthe shift lever.

According to the present invention, in a case where the first detectionunit is abnormal, if the position of the shift lever is maintained untila predetermined second time longer than the first time elapses, theshift position of the transmission is switched to the shift positioncorresponding to the position of the shift lever. This can reliablyprevent erroneous determination of the shift position based on theposition of the shift lever.

More preferably, the shift lever is a momentary-type shift lever.

According to the present invention, the parking lock can be releasedaccording to the intention of a driver even when there occurs anabnormality in the first detection unit, by applying the presentinvention to a momentary-type shift lever.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a configuration of a shift control system 10 in accordancewith the present embodiment.

FIG. 2 shows a configuration of a shift switching mechanism of FIG. 1.

FIG. 3 shows a configuration of a shift lever mechanism.

FIG. 4 shows regions for determining shift positions (part 1).

FIG. 5 shows states of abnormalities in a select sensor.

FIG. 6 shows shift positions read differently in the event of anabnormality.

FIG. 7 shows regions for determining shift positions (part 2).

FIG. 8 shows regions for determining shift positions (part 3).

FIG. 9 is a functional block diagram of an HV-ECU of a shift switchingdevice in accordance with a first embodiment.

FIG. 10 is a flowchart showing a control structure of a program executedby the HV-ECU of the shift switching device in accordance with the firstembodiment.

FIG. 11 is a timing chart showing operation of the HV-ECU of the shiftswitching device in accordance with the first embodiment.

FIG. 12 shows regions for determining shift positions in a left-handdrive vehicle (part 1).

FIG. 13 shows regions for determining shift positions in a left-handdrive vehicle (part 2).

FIG. 14 shows a plurality of combinations of shift positions readdifferently in the event of an abnormality.

FIG. 15 is a flowchart showing a control structure of a program executedby an HV-ECU of a shift switching device in accordance with a secondembodiment.

FIG. 16 is a timing chart showing operation of the HV-ECU of the shiftswitching device in accordance with the second embodiment.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described withreference to the drawings. In the following description, identical partswill be designated by the same reference numerals. Since names andfunctions thereof are also the same, detailed description thereof willnot be repeated.

First Embodiment

FIG. 1 shows a configuration of a shift control system 10 serving as ashift switching device in accordance with the present embodiment. Shiftcontrol system 10 in accordance with the present embodiment is used toswitch a shift position of a vehicle. In the present embodiment,description will be given taking a hybrid vehicle as an example of avehicle equipped with shift control system 10. However, the vehicle isnot particularly limited to a hybrid vehicle, and any vehicle may beused as long as it is equipped with shift control system 10 switching ashift position of a transmission (in particular, switching betweenactuation and release of a parking lock) using at least drive force ofan actuator.

Shift control system 10 includes a P switch 20, a shift lever mechanism26, an HV (Hybrid Vehicle)—ECU (Electronic Control Unit) 30, a parkingcontrol device (hereinafter referred to as a “P-ECU”) 40, an actuator42, an encoder 46, a shift switching mechanism 48, a meter ECU 50, and ameter 52. Shift control system 10 functions as a shift-by-wire systemswitching a shift position by electric control. Specifically, shiftswitching mechanism 48 is driven by actuator 42 to switch a shiftposition.

P switch 20 is a switch for switching a shift position between a parkingposition (hereinafter referred to as a “P position”) and positions otherthan the parking position (hereinafter referred to as “non-Ppositions”). A driver inputs an instruction to switch a shift positionto the P position via P switch 20. P switch 20 may be a momentaryswitch. A P command signal indicating the instruction from the driverreceived by P switch 20 is transmitted to HV-ECU 30. It is to be noted ashift position may be switched from a non-P position to the P positionby a component other than P switch 20 as described above.

Shift lever mechanism 26 includes a shift lever (not shown), a shiftgate (not shown), a select sensor 22, and a shift sensor 24. The shiftlever is moved along a passage formed in the shift gate. In the shiftgate, positions corresponding to shift positions such as a forward driveposition (hereinafter referred to as a “D position”), a reverse driveposition (hereinafter referred to as an “R position”), a neutralposition (hereinafter referred to as an “N position”), and a brakeposition (hereinafter referred to as a “B position”) are set beforehand.Select sensor 22 detects a position of the shift lever in a selectdirection. Select sensor 22 transmits to HV-ECU 30 a signal indicatingthe detected position in the select direction. Shift sensor 24 detects aposition of the shift lever in a shift direction. Shift sensor 24transmits to HV-ECU 30 a signal indicating the detected position in theshift direction. The select direction and the shift direction will bedescribed later.

HV-ECU 30 manages entire operation of shift control system 10.Specifically, when HV-ECU 30 receives the P command signal from P switch20, HV-ECU 30 transmits a P request signal to P-ECU 40. HV-ECU 30 alsodetermines a shift position corresponding to the position of the shiftlever based on detection results from select sensor 22 and shift sensor24. When the shift position is determined, HV-ECU 30 performs controlswitching a shift position in a transmission (not shown) to thedetermined shift position, and transmits to meter ECU 50 a displaycontrol signal indicating the state of the current shift position. It isto be noted that, although the transmission in the present embodiment isa transmission configured of a continuously variable transmissionmechanism, it may be configured of a gear-type transmission mechanism.

Further, for example when a shift position is the parking position andthe shift position determined by the position of the shift lever is anyof the D position, N position, and R position, HV-ECU 30 transmits anon-P request signal to P-ECU 40. HV-ECU 30 is connected (for example toa CAN (Controller Area Network)) such that it can mutually communicatewith P-ECU 40 and meter ECU 50.

Meter ECU 50 transmits to meter 52 the display control signal fromHV-ECU 30 for an instruction or a warning to the driver. Meter 52displays the state of equipment of the vehicle, the state of the shiftposition, and the like.

When P-ECU 40 receives a P request signal or a non-P request signal fromHV-ECU 30, P-ECU 40 controls operation of actuator 42 driving shiftswitching mechanism 48 to switch the shift position from one to theother of the P position and a non-P position, and transmits to HV-ECU 30a signal indicating whether the current shift position is the P positionor a non-P position.

If the driver performs manipulation corresponding to transmission of a Pcommand signal at P switch 20 (for example, presses a button) when theshift position is a non-P position, P-ECU 40 receives a P request signalfrom HV-ECU 30 and switches the shift position from the non-P positionto the P position. P-ECU 40 also transmits to HV-ECU 30 a signalindicating that the current shift position is the P position. Based onthe received signal, HV-ECU 30 transmits to meter 52 via meter ECU 50 adisplay control signal for performing display corresponding to the Pposition. Based on the received display control signal, meter 52displays that the current shift position is the P position. It is to benoted that P-ECU 40 may transmit to meter ECU 50 a display controlsignal for causing meter 52 to perform display corresponding to the Pposition.

Actuator 42 is configured of a switched reluctance motor (hereinafterreferred to as an “SR motor”), and receives an actuator control signalfrom P-ECU 40 and drives shift switching mechanism 48. Although actuator42 will be described as an actuator configured of a motor in the presentinvention, it may be a hydraulically operated actuator. Encoder 46rotates integrally with actuator 42, and detects the rotation state ofthe SR motor. Encoder 46 of the present embodiment is a rotary encoderoutputting A-phase, B-phase, and Z-phase signals. P-ECU 40 obtains thesignals output from encoder 46 to grasp the rotation state of the SRmotor, and performs control of energization for driving the SR motor.

FIG. 2 shows a configuration of shift switching mechanism 48.Hereinafter, description will be given on the assumption that the shiftposition refers to the P position and the non-P position, and does notinclude the R, N, and D positions as non-P positions. However, the R, N,and D positions may be included. Specifically, although description willbe given in the present embodiment on a two-position configurationhaving the P position and the non-P position, a four-positionconfiguration having the P position and non-P positions including the R,N, and D positions may be employed.

Shift switching mechanism 48 includes a shaft 102 rotated by actuator42, a detent plate 100 rotated according to rotation of shaft 102, a rod104 operated according to rotation of detent plate 100, a parking lockgear 108 fixed to an output shaft of a transmission not shown, a parkinglock pole 106 for locking parking lock gear 108, and a detent spring 110and a roller 112 limiting the rotation of detent plate 100 and fixing ashift position. Detent plate 100 is driven by actuator 42 to switch ashift position. Further, encoder 46 functions as counting meansobtaining a counted value corresponding to the rotation amount ofactuator 42.

FIG. 2 shows a state where the shift position is the non-P position.Since parking lock pole 106 does not lock parking lock gear 108 in thisstate, rotation of a drive shaft of the vehicle is not prevented. Whenshaft 102 is rotated by actuator 42 in a clockwise direction from thisstate, rod 104 is pushed via detent plate 100 in a direction indicatedby an arrow A shown in FIG. 2, and parking lock pole 106 is pushed up bya tapered portion provided at a tip end of rod 104 in a directionindicated by an arrow B shown in FIG. 2. According to the rotation ofdetent plate 100, roller 112 of detent spring 110 located at one of twovalleys provided at the top of detent plate 100, that is, a non-Pposition location 120, passes over a peak 122 and moves to the othervalley, that is, a P position location 124. Roller 112 is provided todetent spring 110 to be rotatable about an axial direction thereof. Whendetent plate 100 is rotated to allow roller 112 to be located at Pposition location 124, parking lock pole 106 is pushed up to a positionwhere a projected portion of parking lock pole 106 engages between teethof parking lock gear 108. Thereby, the drive shaft of the vehicle ismechanically secured, and the shift position is switched to the Pposition.

In shift control system 10 in accordance with the present embodiment,P-ECU 40 controls the rotation amount of actuator 42 so as to reduceimpact given when roller 112 of detent spring 110 falls after passingover peak 122, in order to reduce load on the components of the shiftswitching mechanism such as detent plate 100, detent spring 110, andshaft 102, applied when the shift position is switched.

Actuator 42 rotates detent plate 100 provided to manual shaft 102.Rotations in predetermined directions are respectively defined by a Pwall 200 and a non-P wall 210 formed in detent plate 100.

As shown in FIG. 3, shift lever mechanism 26 includes a shift gate 262and a shift lever 264. In the present embodiment, shift lever 264 is amomentary type shift lever. Specifically, the driver can move shiftlever 264 along a path formed in shift gate 262, using an M position inFIG. 3 as a reference position. In the present embodiment, shift gate262 corresponds to a shift gate of a right-hand drive vehicle.

In a case where the driver does not apply manipulation force to shiftlever 264, shift lever 264 automatically returns to the M position asthe reference position by means of a mechanical mechanism utilizing aspring or the like provided to shift lever 264. Since the structure andoperation of a momentary type shift lever are well-known techniques,detailed description thereof will not be provided.

In addition to the M position, shift gate 262 is provided with the Rposition, N position, D position, and B position. In the presentembodiment, the shift direction refers to an up-down direction on apaper plane of FIG. 3. In shift gate 262, the R position and the Dposition are associated with positions at both ends of a shift passage(1) 266 formed along the shift direction. The N position is associatedwith a position in the middle of shift passage (1) 266.

In the present embodiment, the select direction refers to a left-rightdirection on the paper plane of FIG. 3. A select passage 268 having oneend connected to the position of the N position in shift passage (1) 266is further formed in shift gate 262 along the select direction. The Mposition is associated with a position at the other end of selectpassage 268.

In addition, a shift passage (2) 270 having one end connected to theposition of the M position in select passage 268 is further formed inshift gate 262 along the shift direction. The B position is associatedwith the other end of shift passage (2) 270 in a lower direction on thepaper plane of FIG. 3.

In a case where shift lever 264 is moved by the driver from the Mposition to a specific shift position, and the position of shift lever264 is maintained at the move destination position until a predeterminedtime Tn(1) elapses, HV-ECU 30 determines the shift positioncorresponding to the move destination position. In the presentembodiment, the select direction corresponds to a first direction, andthe shift direction corresponds to a second direction.

Select sensor 22 transmits to HV-ECU 30 a voltage signal correspondingto the position of shift lever 264 in the select direction. In thepresent embodiment, select sensor 22 outputs a voltage within a rangefrom a lower limit value V_Lo(1) to an upper limit value V_Hi(1)corresponding to boundaries of a range in which shift lever 264 ismovable in the select direction. Lower limit value V_Lo(1) and upperlimit value V_Hi(1) are each an output voltage value within a range ofat least 0 V to 10 V.

The relation between the position of shift lever 264 in the selectdirection and the voltage is, for example, a linear relation. The aboverelation may not be a linear relation if the position of shift lever 264in the select direction can be computed based on an output voltage valueof select sensor 22.

Shift sensor 24 transmits to HV-ECU 30 a voltage signal corresponding tothe position of shift lever 264 in the shift direction. In the presentembodiment, shift sensor 24 outputs a voltage within a range from alower limit value V_Lo(2) to an upper limit value V_Hi(2) correspondingto boundaries of a range in which shift lever 264 is movable in theshift direction. Lower limit value V_Lo(2) and upper limit value V_Hi(2)are each an output voltage value within a range of at least 0 V to 10 V.

The relation between the position of shift lever 264 in the shiftdirection and the voltage is, for example, a linear relation. The aboverelation may not be a linear relation if the position of shift lever 264in the shift direction can be computed based on an output voltage valueof shift sensor 24.

HV-ECU 30 determines the position of shift lever 264 in shift gate 262based on an output voltage corresponding to the position thereof in theselect direction received from select sensor 22 and an output voltagecorresponding to the position thereof in the shift direction receivedfrom shift sensor 24.

In a case where the position of shift lever 264 is moved to a shiftposition other than the M position in shift gate 262, and shift lever264 is maintained at the move destination position until predeterminedtime Tn(1) elapses, HV-ECU 30 determines the shift positioncorresponding to the move destination position.

In a memory of HV-ECU 30, for example, a map indicating the relationamong the output voltage value of select sensor 22, the output voltagevalue of shift sensor 24, and the shift positions as shown in FIG. 4 isstored beforehand.

As shown in FIG. 4, upper limit value V_Hi(1) and lower limit valueV_Lo(1) of the output voltage are set for the boundaries of the range inwhich shift lever 264 is movable in the select direction. Upper limitvalue V_Hi(1) and lower limit value V_Lo(1) are predetermined outputvoltage values. They are not particularly limited, and adapted throughdesign or experiments.

In addition, a threshold value V_Mid(1) is set between upper limit valueV_Hi(1) and lower limit value V_Lo(1). A 0 V side is indicated in aright direction on a paper plane of FIG. 4. Upper limit value V_Hi(1),threshold value V_Mid(1), and lower limit value V_Lo(1) are set withinthe range between 0 V and 10 V.

Similarly, upper limit value V_Hi(2) and lower limit value V_Lo(2) ofthe output voltage are set for the boundaries of the range in whichshift lever 264 is movable in the shift direction. A 0 V side isindicated in an upper direction on the paper plane of FIG. 4. Upperlimit value V_Hi(2) and lower limit value V_Lo(2) are predeterminedoutput voltage values. They are not particularly limited, and adaptedthrough design or experiments.

In addition, a threshold value V_Mid(2) and a threshold value V_Mid(3)greater than V_Mid(2) are set between upper limit value V_Hi(2) andlower limit value V_Lo(2). The 0 V side is indicated in the upperdirection on the paper plane of FIG. 4. Upper limit value V_Hi(2),threshold values V_Mid(2) and V_Mid(3), and lower limit value V_Lo(2)are set in the range between 0 V and 10 V.

For example, lower limit values V_Lo(1) and V_Lo(2) may be set to 0 V,and upper limit values V_Hi(1) and V_Hi(2) may be set to 10 V. Thresholdvalues V_Mid(1) to V_Mid(3) are predetermined output voltage values.They are not particularly limited, and adapted through design orexperiments.

As shown in FIG. 4, separated six regions are set by V_Hi(1), V_Mid(1),and V_Lo(1) in the select direction and V_Hi(2), V_Mid(2), V_Mid(3), andV_Lo(2) in the shift direction. The shift positions are associated withthe separated six regions to match the shape of shift gate 262.Specifically, the R position, the N position, the D position, an M′position, the M position, and the B position are associated with theseparated six regions. The M′ position shown in a hatched region in FIG.4 is a region that does not correspond to any of a plurality of shiftpositions of the transmission.

In the present embodiment, the R position is associated with a regionthat is between V_Lo(1) and V_Mid(1) in the select direction and betweenV_Lo(2) and V_Mid(2) in the shift direction.

The N position is associated with a region that is between V_Lo(1) andV_Mid(1) in the select direction and between V_Mid(2) and V_Mid(3) inthe shift direction.

The D position is associated with a region that is between V_Lo(1) andV_Mid(1) in the select direction and between V_Mid(3) and V_Hi(2) in theshift direction.

The M′ position is associated with a region that is between V_Mid(1) andV_Hi(1) in the select direction and between V_Lo(2) and V_Mid(2) in theshift direction.

The M position is associated with a region that is between V_Mid(1) andV_Hi(1) in the select direction and between V_Mid(2) and V_Mid(3) in theshift direction.

The B position is associated with a region that is between V_Mid(1) andV_Hi(1) in the select direction and between V_Mid(3) and V_Hi(2) in theshift direction.

HV-ECU 30 determines the shift position corresponding to the position ofshift lever 264 as described above based on the voltage signals outputfrom select sensor 22 and shift sensor 24, and controls the transmissionto switch to the determined shift position.

The present invention is characterized in that, in the vehicle having astructure as described above, HV-ECU 30 determines whether or not selectsensor 22 is abnormal, and in a case where it determines that selectsensor 22 is abnormal, HV-ECU 30 changes the shift positioncorresponding to the position of shift lever 264 to a shift positionreleasing the parking position.

HV-ECU 30 determines whether or not select sensor 22 is abnormal basedon the detection result of select sensor 22. In the present embodiment,HV-ECU 30 determines whether or not select sensor 22 is abnormal basedon the state of the voltage output from select sensor 22. In the presentembodiment, shift sensor 24 includes two sensors, and output voltagevalues V_a and V_b are output from the respective sensors to HV-ECU 30.Further, select sensor 22 includes two sensors, and output voltagevalues V_c and V_d are output from the respective sensors to HV-ECU 30.

As shown in FIG. 5, in a case where both output voltage values V_c andV_d of select sensor 22 are lower than V_Lo(1), HV-ECU 30 determinesthat there occurs an abnormality that the output voltage is fixed on alow side due to a break or a short circuit to ground (GND short circuit)in select sensor 22.

In a case where both output voltage values V_c and V_d of select sensor22 are higher than V_Hi(1), HV-ECU 30 determines that there occurs anabnormality that the output voltage is fixed on a high side due to ashort circuit inside select sensor 22.

Further, in a case where output voltage values V_c and V_d of selectsensor 22 are different from each other, HV-ECU 30 determines that thereoccurs an abnormality of logical inconsistency.

Alternatively, in a case where the position of shift lever 264 specifiedby the position in the select direction is not a position correspondingto the shift position of the transmission in relation to the position inthe shift direction, HV-ECU 30 may determine that select sensor 22 isabnormal.

For example, HV-ECU 30 determines that select sensor 22 is abnormal in acase where it determines that shift lever 264 is within the region ofthe M′ position based on the output voltage values of select sensor 22and shift sensor 24.

Although abnormality of select sensor 22 is determined by detectingfixation on the low side, fixation on the high side, logicalinconsistency, and the M′ position, abnormality of select sensor 22 maybe determined by any of the above techniques, or may be determined bycombining two or more of the above techniques.

When HV-ECU 30 determines that select sensor 22 is abnormal, HV-ECU 30changes a shift position corresponding to the position of shift lever264 when select sensor 22 is normal.

For example, as shown in FIG. 6, the positions of shift lever 264associated with the M position and the N position when select sensor 22is normal are both read as the M position when select sensor 22 isabnormal.

Further, the positions of shift lever 264 associated with the shiftpositions related to the driving of the vehicle (for example, the Rposition, the D position, and the B position) when the select sensor isnormal are all read as the N position when select sensor 22 is abnormal.Preferably, it is desirable that the M′ position is read as the Nposition.

With such a configuration, for example, in a case where the outputvoltage of select sensor 22 is fixed on the low side, only a pathindicated by hatched lines in FIG. 7 can be detected, and thus HV-ECU 30cannot determine the shift positions other than the R position, the Nposition, and the D position. In this case, the position of the Nposition in the normal state is read as the M position by reading theshift position differently using the map shown in FIG. 6. If shift lever264 is moved to the D position or the R position in the normal state onthis occasion, the shift position is read as the N position, and thusthe parking position can be released.

Alternatively, in a case where the output voltage of select sensor 22 isfixed on the high side, only a path indicated by hatched lines in FIG. 8can be detected, and thus HV-ECU 30 cannot determine the shift positionsother than the M′ position, the M position, and the B position. In thiscase, the positions of the M′ position and the B position in the normalstate are read as the N position by reading the shift positionsdifferently using the map shown in FIG. 6. If shift lever 264 is movedto the B position in the normal state on this occasion, the shiftposition is read as the N position, and thus the parking position can bereleased. Alternatively, even if shift lever 264 is moved to the Rposition but erroneously determined as the M′ position, the shiftposition is read as the N position, and thus the parking position can bereleased.

FIG. 9 shows a functional block diagram of HV-ECU 30 of the shiftswitching device in accordance with the present embodiment. HV-ECU 30includes an input interface (hereinafter referred to as an input I/F)300, a processing unit 400, a storage unit 500, and an output interface(hereinafter referred to as an output I/F) 600.

Input I/F 300 receives a select direction position detection signal(i.e., a signal for detecting the position in the select direction) fromselect sensor 22, and a shift direction position detection signal (i.e.,a signal for detecting the position in the shift direction) from shiftsensor 24.

Processing unit 400 includes a select sensor abnormality determinationunit 402, a fail-safe processing unit 404, a timer unit 406, a shiftdetermination unit 408, a request signal output unit 410, and a metercontrol unit 412.

Select sensor abnormality determination unit 402 determines whether ornot select sensor 22 is abnormal based on the detection result of selectsensor 22. Since the method of determining abnormality of select sensor22 is as described above, detailed description thereof will not berepeated. When select sensor abnormality determination unit 402determines that select sensor 22 is abnormal, select sensor abnormalitydetermination unit 402 turns on a select sensor abnormalitydetermination flag.

When select sensor 22 is determined as abnormal, fail-safe processingunit 404 performs fail-safe processing. Specifically, fail-safeprocessing unit 404 turns on a fail-safe permission flag simultaneouslywhen the select sensor abnormality determination flag is turned on. Onthis occasion, fail-safe processing unit 404 changes the shift positioncorresponding to the position of shift lever 264 when select sensor 22is normal, as shown in FIG. 6. Fail-safe processing unit 404 may performfail-safe processing when the select sensor abnormality determinationflag is on.

Timer unit 406 measures a time that elapses after the position of shiftlever 264 is stopped. In the present embodiment, for example, timer unit406 counts stop times at the N position and the M position. The stop ofthe position of shift lever 264 may be determined based on the outputvoltage values of select sensor 22 and shift sensor 24. For example,timer unit 406 may reset a count value to an initial value wheneverthere is a change in the output voltage value of select sensor 22 orshift sensor 24. When measurement of the elapsed time is started, timerunit 406 increments the count value by a predetermined value for eachcalculation cycle.

Shift determination unit 408 determines whether or not the shiftposition read differently using the detection results of select sensor22 and shift sensor 24 and the map shown in FIG. 6 is the N position.Specifically, when a time that elapses after the position of shift lever264 is stopped at a position corresponding to a shift position read asthe N position is equal to or longer than a predetermined standby timeTn(2), shift determination unit 408 determines that the shift positionis the N position.

When select sensor 22 is abnormal, if the position of shift lever 264 isstopped at the position corresponding to the N position and maintaineduntil predetermined standby time Tn(2) longer than standby time Tn(1) inthe normal state elapses, shift determination unit 408 determines thatthe shift position is the N position. It is to be noted that, forexample, if the fail-safe permission flag is on, shift determinationunit 408 may change standby time Tn(1) to standby time Tn(2).

When the shift position is determined as the N position, request signaloutput unit 410 generates a non-P request signal, and transmits thenon-P request signal to P-ECU 40 via output I/F 600. P-ECU 40 receivesthe non-P request signal, and if the position of roller 112 based on therotation amount of shaft 102 detected by encoder 46 is P positionlocation 124, P-ECU 40 transmits to actuator 42 a control signal to moveroller 112 to non-P position location 120.

Meter control unit 412 generates a display control signal correspondingto the determined shift position, and transmits the display controlsignal to meter ECU 50 via output I/F 600. Meter ECU 50 causes meter 52to display the contents corresponding to the received display controlsignal. Alternatively, meter ECU 50 turns on a desired indication lampof meter 52.

In the present embodiment, although select sensor abnormalitydetermination unit 402, fail-safe processing unit 404, timer unit 406,shift determination unit 408, and request signal output unit 410 areeach described as functioning as software implemented by a CPU asprocessing unit 400 executing a program stored in storage unit 500, theymay be implemented by hardware. Such a program is recorded in a storagemedium and mounted in the vehicle.

Storage unit 500 stores various information, programs, threshold values,maps, and the like, and data is read by processing unit 400 or storedfrom processing unit 400, if needed.

Hereinafter, a control structure of a program executed by HV-ECU 30 ofthe shift switching device in accordance with the present embodimentwill be described with reference to FIG. 10.

In step (hereinafter referred to as “S”) 100, HV-ECU 30 determineswhether or not select sensor 22 is abnormal. If select sensor 22 isabnormal (YES in S100), the processing proceeds to S102. Otherwise (NOin S100), the processing returns to S100.

In S102, HV-ECU 30 turns on a fail-safe permission flag. In S104, HV-ECU30 determines whether or not the shift position read differently usingthe map shown in FIG. 6 when select sensor 22 is abnormal is the Nposition. If the shift position is read as the N position (YES in S104),the processing proceeds to S106. Otherwise (NO in S104), the processingreturns to S104.

In S106, HV-ECU 30 determines whether or not the position of shift lever264 is maintained until predetermined time Tn(2) elapses. If theposition of shift lever 264 is maintained until predetermined time Tn(2)elapses (YES in S106), the processing proceeds to S108. Otherwise (NO inS106), the processing returns to S104.

In S108, HV-ECU 30 outputs an non-P request signal to P-ECU 40.

Operation of HV-ECU 30 of the shift switching device in accordance withthe present embodiment based on the structure and the flowchart asdescribed above will be described with reference to FIG. 11.

When there occurs an abnormality in the detection result of selectsensor 22 at a time T(0), abnormality of select sensor 22 is determinedat a time T(1) (YES in S100), and a select sensor abnormalitydetermination flag is turned on. On this occasion, a fail-safepermission flag is turned on, and fail-safe processing is performed(S102).

When shift lever 264 is moved to a position corresponding to any shiftposition among the R position, the D position, and the B position by thedriver's manipulation at a time T(2), the shift position is readdifferently and determined as the N position (YES in S104).

At a time T(3) when predetermined time Tn(2) elapses after the shiftposition is determined as the N position, it is determined that theshift position is the N position. On this occasion, HV-ECU 30 outputs annon-P request signal to P-ECU 40. When P-ECU 40 receives the non-Prequest signal, the position of roller 112 is moved to non-P positionlocation 124 by rotation force of actuator 42. As a result, theprojected portion of parking lock pole 106 is moved away from the teethof parking lock gear 108, and thereby the parking lock is released.

When the driver stops applying manipulation force to shift lever 264 ata time T(4), shift lever 264 returns to the position corresponding tothe M position.

As has been described above, according to the shift switching device inaccordance with the present embodiment, by changing at least one of aplurality of shift positions specified by detecting the position of theshift lever in the shift direction to the neutral position, the shiftposition can be reliably switched to the neutral position, which is theshift position releasing the parking position, by manipulating the shiftlever. Thereby, switching from the parking position to the neutralposition can be performed even when there occurs an abnormality in theselect sensor. Thus, the parking lock can be released according to theintention of the driver. As a result, the vehicle can be moved by beingpushed with hands or using a tow truck or the like. Therefore, a shiftswitching device that releases a parking lock according to the intentionof a driver even in the event of an abnormality in a sensor duringdetection of the position of a shift lever can be provided.

Further, the HV-ECU determines whether or not the select sensor isabnormal based on the state of the voltage output from the select sensor(for example, voltage's fixation on the low side or fixation on the highside, a difference in the output voltage values of the two sensors, orthe like). Thereby, whether or not the select sensor is abnormal can bedetermined with high accuracy.

Further, switching the shift position when the select sensor is abnormaland the position of the shift lever is maintained until standby timeTn(2) longer than standby time Tn(1) elapses can reliably preventerroneous determination of the shift position based on the position ofthe shift lever. It is to be noted that standby time Tn(1) and standbytime Tn(2) may be the same. With such a configuration, the driver isless likely to feel uncomfortable.

In a case where the select sensor is abnormal and in addition the shiftposition is the parking position, the HV-ECU may change the shiftposition corresponding to the position of the shift lever. With such aconfiguration, the shift position can be reliably switched to theneutral position by manipulating the shift lever even when there occursan abnormality in the select sensor. Thus, the parking lock can bereleased according to the intention of the driver.

Although the present embodiment has described an exemplary case wherethe present invention is applied to a right-hand drive vehicle, thepresent invention is not particularly limited thereto, and may beapplied, for example, to a left-hand drive vehicle.

For example, in a left-hand drive vehicle, the shift gate has a shapesymmetrical to that of shift gate 262 of the right-hand drive vehicle.

Therefore, for example, in a case where the output voltage of selectsensor 22 is fixed on the low side, only a path indicated by hatchedlines in FIG. 12 can be detected, and thus HV-ECU 30 cannot determinethe shift positions other than the M′ position, the M position, and theB position. In this case, the positions of the M′ position and the Bposition in the normal state are read as the N position by reading theshift positions differently using the map shown in FIG. 6. If shiftlever 264 is moved to the B position in the normal state on thisoccasion, the shift position is read as the N position, and thus theparking position can be released. Alternatively, even if the shift leveris moved to the R position but erroneously determined as the M′position, the shift position is read as the N position, and thus theparking position can be released.

Further, in a case where the output voltage of select sensor 22 is fixedon the high side, only a path indicated by hatched lines in FIG. 13 canbe detected, and thus HV-ECU 30 cannot determine the shift positionsother than the R position, the N position, and the D position. In thiscase, the position of the N position in the normal state is read as theM position by reading the shift position differently using the map shownin FIG. 6. If shift lever 264 is moved to the D position or the Rposition in the normal state on this occasion, the shift position isread as the N position, and thus the parking position can be released.

Therefore, the shift position can be reliably switched to the N positionby the driver's manipulation of shift lever 264, the parking lock can bereleased.

Further, although the present embodiment has described the case wherethe N position is read as the M position and a plurality of other shiftpositions related to the driving of the vehicle are read as the Nposition as shown in FIG. 6, the present invention is not particularlylimited to such a reading manner.

For example, the shift position may be changed using any of patterns (A)to (E) as shown in FIG. 14. Alternatively, one of patterns (A) to (E)may be selected according to the state of the abnormality of selectsensor 22 (for example, fixation on the low side, fixation on the highside, or logical inconsistency). With this configuration, a readingrange can be set according to the state of the abnormality.

Pattern (A) is a pattern in which only the M′ position is read as the Nposition. Pattern (B) is a pattern in which the D position and the Bposition are read as the N position. Pattern (C) is a pattern in whichonly the R position is read as the N position.

Pattern (D) is a pattern in which the R position, the D position, the Bposition, and the M′ position are read as the N position. When comparedwith FIG. 6, pattern (D) is different in that the shift position for theN position is not changed.

Pattern (E) is a pattern in which the R position, the D position, andthe B position are read as the N position. The same effect as thatdescribed above can also be obtained by using the shift position usingany of patterns (A) to (E).

Second Embodiment

A shift switching device in accordance with a second embodiment will nowbe described. When compared with the configuration of the shiftswitching device in accordance with the first embodiment describedabove, the shift switching device in accordance with the presentembodiment is different in the control structure of a program executedby HV-ECU 30. Other than that, the shift switching device in accordancewith the present embodiment has the same configuration as that of theshift switching device in accordance with the first embodiment describedabove. They will be designated by the same reference numerals. Sincenames and functions thereof are also the same, detailed descriptionthereof will not be repeated here.

In the present embodiment, HV-ECU 30 is characterized in that, in a casewhere select sensor 22 is abnormal and in addition the position of shiftlever 264 is maintained at the reference position until a predeterminedtime Tm elapses, HV-ECU 30 changes the shift position corresponding tothe position of the shift lever. Specifically, HV-ECU 30 determineswhether or not the position of shift lever 264 is maintained untilpredetermined time Tm elapses after a select sensor abnormalitydetermination flag is turned on. When the position of shift lever 264 ismaintained at the M position as the reference position untilpredetermined time Tm elapses, HV-ECU 30 turns on a fail-safe permissionflag.

Hereinafter, a control structure of a program executed by HV-ECU 30 ofthe shift switching device in accordance with the present embodimentwill be described with reference to FIG. 15.

It is to be noted that the same step number is given to the sameprocessing in the flowcharts of FIGS. 10 and 15, and what is processedin those steps is also the same. Therefore, detailed description thereofwill not be repeated here.

If select sensor 22 is determined as abnormal (YES in S100), HV-ECU 30determines in S200 whether or not shift lever 264 is maintained at thereference position until predetermined time Tm elapses. If shift lever264 is maintained at the reference position until predetermined time Tmelapses (YES in S200), the processing proceeds to S102. Otherwise (NO inS200), the processing returns to S200.

Operation of HV-ECU 30 of the shift switching device in accordance withthe present embodiment based on the structure and the flowchart asdescribed above will be described with reference to FIG. 16.

When there occurs an abnormality in the detection result of selectsensor 22 at time T(0), abnormality of select sensor 22 is determined attime T(1) (YES in S100), and a select sensor abnormality determinationflag is turned on. It is determined whether or not the position of shiftlever 264 is maintained at the M position until predetermined time Tmelapses from when the select sensor abnormality determination flag isturned on (S200).

Since it is determined at a time T′(1), which is a time point whenpredetermined time Tm elapses from time T(1), that the position of shiftlever 264 is maintained at the M position until predetermined time Tmelapses (YES in S200), a fail-safe permission flag is turned on andfail-safe processing is performed (S102).

It is to be noted that, since the operation of the shift switchingdevice at times T(2) to T(4) and thereafter is the same as the operationof the shift switching device at times T(2) to T(4) and thereafter inthe shift switching device described using FIG. 11, detailed descriptionthereof will not repeated.

As has been described above, according to the shift switching device inaccordance with the present embodiment, in a case where the position ofthe shift lever is maintained at the reference position until apredetermined time elapses after the selector sensor is determined asabnormal, such a case can be determined as not being in a state wherethe shift lever is erroneously manipulated (for example, a state wherean object is hung on the lever). By changing the shift positioncorresponding to the position of the shift lever to a shift positionreleasing the parking position (for example, the neutral position) onthis occasion, the shift position can be reliably switched to theneutral position by manipulating the shift lever. Thus, the parking lockcan be released according to the intention of the driver. As a result,the vehicle can be moved by being pushed with hands or using a tow truckor the like. Therefore, a shift switching device that releases a parkinglock according to the intention of a driver even in the event of anabnormality in a sensor during detection of the position of a shiftlever can be provided.

It should be understood that the embodiments disclosed herein areillustrative and non-restrictive in every respect. The scope of thepresent invention is defined by the scope of the claims, rather than thedescription above, and is intended to include any modifications withinthe scope and meaning equivalent to the scope of the claims.

The invention claimed is:
 1. A shift switching device comprising a first detection unit detecting a position of a shift lever in a first direction and a second detection unit detecting a position of said shift lever in a second direction, for switching a shift position of a transmission mounted in a vehicle based on the position in the first direction and the position in the second direction, wherein said shift position includes at least a parking position and a shift position different from said parking position, wherein said shift switching device further comprises a processing unit specifying a shift position based on detection results of said first detection unit and said second detection unit, and said processing unit determines whether or not said first detection unit is abnormal, and in a case where said processing unit determines that said first detection unit is abnormal; and said shift switching device releases said parking position and if said shift lever is not manipulated in said second direction; maintains said parking position.
 2. The shift switching device according to claim 1, wherein said shift lever is a momentary-type shift lever which automatically returns to a reference position when no manipulation force is applied, and if said shift lever is maintained at a move destination position from said reference position until a predetermined time elapses, a shift position corresponding to said move destination position is determined. 